VBXE 2

[Roydea6]

candle,

After reading the horror stories here about desoldering. I was wondering if the 130xe version of vbxe2 will fit into my fully socketed 800xl. I realize the I would still need to desolder the existing socket, in order to put in the machined one.

 

Same question for all the XL's.

 

 

 

[candle]

and then make a support for keyboard, as unit wouldn't close...

look on installation thread - most of those boards are already installed

two persons had problems and a big ones, why? because of lack of experience, or wrong tooling

this is not rocket science, using common sense will keep you away from a disaster

(ie if its stuck, then its not desoldered, do not pull like your life would depend on it)

[+orpheuswaking]

and then make a support for keyboard, as unit wouldn't close...

look on installation thread - most of those boards are already installed

two persons had problems and a big ones, why? because of lack of experience, or wrong tooling

this is not rocket science, using common sense will keep you away from a disaster

(ie if its stuck, then its not desoldered, do not pull like your life would depend on it)

 

Now now candle, play nice

 

the 130XE is a bitch to desolder if you are not very careful and not familiar with how easy it is to lift traces. Just take care and lots of patience.

[mimo]

 

You know, if you all dream about being expert soldering techs then jump on in, but I think we would do better as a community (and save a few boards) if the software types did software and the user types did using and the hardware types did the heavy lifting in the solder department. Atari folks write all kinds of software that I get to use, and keep me up on all the cool stuff our machines can do - all for free. I would think that something could be worked out where an Atari board could be packed in a return box (with postage) and then shipped in an outer box to a hardware guy for him to do something simple, like add a socket or pull a part. I know I could have done 10 sockets just in the time it took me to write this.

 

 

 

great idea:thumbsup:

[+Stephen]

 

Now now candle, play nice

 

the 130XE is a bitch to desolder if you are not very careful and not familiar with how easy it is to lift traces. Just take care and lots of patience.

I can vouch for that! I used to have a full time job at a small PCB place populating, wave soldering, and repairing custom boards for years. I can solder SMD stuff just fine, and even I trashed (not beyond repair at least) some 130XE boards. These things are the biggest pile of $hit quality wise I have ever worked on.

 

Stephen Anderson

[+orpheuswaking]

Now now candle, play nice

 

the 130XE is a bitch to desolder if you are not very careful and not familiar with how easy it is to lift traces. Just take care and lots of patience.

I can vouch for that! I used to have a full time job at a small PCB place populating, wave soldering, and repairing custom boards for years. I can solder SMD stuff just fine, and even I trashed (not beyond repair at least) some 130XE boards. These things are the biggest pile of $hit quality wise I have ever worked on.

 

Stephen Anderson

 

Heh, wasn't going to throw you under the bus on this one Stephen, but as you owned up

[Rybags]

Not much joy hooking up the A520 modulator. Modulator is fine with an Amiga, not so with VBXE.

 

Powering it from the PC, checked voltages and they are a fraction over 5/12.

The modulator itself is unmodified other than soldering in wires going to a molex plug to get the power from the PC.

 

Using an adaptor plug to convert the Amiga 9-pin back to 23 pin, with 75 Ohm resistors to ground from the R,G,B. Picture seems exactly like it was before, if not worse.

 

Should the modulator itself be modified to work better? I'm not worried about S-Video or perfect picture just yet, I'd just like to have it working such that I get a reasonable display.

 

[candle]

seems like a lot of noise is comming from power supply

when connected to Amiga, power is taken from db23 plug, right?

can you steal power from Amiga instead of PC so we could exclude that factor from the equasion?

[Rybags]

Amiga packed away but I'll try that later on... got plenty of molex connectors so it'll take 2 minutes to do.

 

The wiring setup I have to the modulator -

R,G,B straight through to DB23 plug, and terminated to common ground of modulator with 75 Ohm resistors.

Tried with and without GND connected through from Atari (same result).

Composite sync straight through to relevant connection.

+5 Volts and +12 Volts from PC to A520 modulator. GND sourced from matching GND on +12 Volt side on PC.

[candle]

ground in respect to rgb signals should be taken directly from apropriate pin of vbxe rgb connector

i would really put out power supply from the equation, since its really noisy

[Rybags]

So, ground the resistors only to the Atari side, and don't bother sharing GND between Atari and the modulator (which gets GND from the PC) ?

[candle]

completly wrong

atari side is already terminated (75R resistors on bottom side of vbxe board) and ground from atari should be connected to ground of rgb input on modulator side

and in that point you need to have another set of terminators (75R resistors)

but it all comes to the quality of 12V line you have there, since its used for analog circuity inside modulator

[Rybags]

Managed a grainy B&W image then it went back to the noisy saturated one - probably best to start from scratch with this adaptor plug.

 

The RGB is grounded via resistors anyway inside the modulator. I don't know if that makes a difference.

 

The RGB first goes inline through 320 Ohm resistors.

 

Then branches off - first set of branches takes each to GND via 1K resistors.

Second branch takes each signal to the MC1377 chip via 22 uF capacitors.

 

Wasn't able to power the A520 from the Amiga and run VBXE through it (don't have the necessary plug) but I tried a setup with the Amiga and A520 powered from the PC and it went fine.

[trub]

Have you tried bypassing the 320ohm resistors ?

[Rybags]

Worth a shot I suppose.

 

According to the MC1377 Datasheet, it will accept RGB over a broad voltage range - it just expects 1V P-P for proper saturation.

 

Might try making another adaptor plug first, although the one I have I tested with multimeter and continuity and expected resistance over all the connections is as expected.

[peteym5]

Just to let everyone know I have obtained a 60w soldering iron, flux paste, and a solder sucker will be here soon. I did some practice on the old board with the 60w iron and does melt the solder more easily. I also have JROKs RPG to S-Video board here so I can display on a TV. I will look into adding a VGA jack later to hook up to a computer monitor.

[Rybags]

I tried something else for the A520 but it just made it worse.

 

Soldered some 82 Ohm resistors in parallel with the 1K ones in the A520 that should give it very close to 75 Ohm termination to ground.

 

No good, so tried wire in parallel with the 320 Ohm resistors such that the path is now RGB input -> wire in parallel with 320R -> ~ 75R termination to GND, capacitors -> RGB inputs of MC1377

 

Even worse. Of course there's the chance the wiring/soldering isn't the best, so many modifications that it's all getting complicated.

 

On the modulator side, would it be best to have the 75 Ohm termination to GND after the capacitors or before them (as is the case now) ?

Edited December 7, 2009 by Rybags

[candle]

what capacitors you have there?

decoupling capacitors? on RGB lines?

[Rybags]

Capacitors are untouched, as per default A520 - 22 uF polar, inline for R/G/B immediately before the MC1377 chip.

 

Couple of pics.

 

 

Also, here's a Datasheet for the MC1377 IC.

 

MC1377.pdf

[candle]

can You measure peak to peak value of RGB inputs before caps?

according to the datasheet you should have 1V p-p for full saturation

i don't know this for sure now, but my guess is VBXE2 output is more to the VGA video standard (0.75Vp-p) which would result in slighty darker image, but not what You've observed

Anyways, You can always compare inputs You get with Amiga and VBXE

[Rybags]

Could be time to get the oscilloscope onto this. Probably leave it for tomorrow.

 

What might be better is if someone could just come up with a simple schematic where you rip the MC1377 out of a 520 and just start afresh and build a small board which could sit in a project box or something.

I've got a protoboard here, so it could well be a lot easier to just take the IC out and use it instead of constantly modifying the A520 to get the thing working nicely.

 

I bought another A520 off eBay, so I can afford to rip the guts out of the one I've already modified.

[Heaven/TQA]

does anybody have a turbo basic test app for vbxe?

[+bob1200xl]

That MC1377 doesn't look like something that you could just throw into a circuit.

 

Be a lot easier for some of us if Candle would just output YPbPr. There are lots and lots of component monitors around.

 

Bob

 

(as if he doesn't have enough to do...)

 

 

 

Could be time to get the oscilloscope onto this. Probably leave it for tomorrow.

 

What might be better is if someone could just come up with a simple schematic where you rip the MC1377 out of a 520 and just start afresh and build a small board which could sit in a project box or something.

I've got a protoboard here, so it could well be a lot easier to just take the IC out and use it instead of constantly modifying the A520 to get the thing working nicely.

 

I bought another A520 off eBay, so I can afford to rip the guts out of the one I've already modified.

[candle]

Tell You what Bob

I'll do RGB->YPbPr converter, and You'll install that damn VBXE into Your computer

Do we have a deal?

[peteym5]

I removed the Antic chip, put the socket in, and put the Antic chip into the socket and now it does not work. I had to re-attach several of the traces. Suspect the new 130xe is probably ruined, not about to go get another one for awhile. I hope I can get it working. Any suggestions.